Water cannon were used in Davos itself and elsewhere in the region police fired tear gas and rubber bullets at demonstrators who were protesting against the World Economic Forum.

Security service spokesman Daniel Reist said water cannon were used on a group of some 100 protesters who had made it into Davos itself, although they were kept contained by the railway station. The spokesman said no-one had been injured, but could not confirm if anyone had been arrested.

Violence also broke out in Landquart, a regional centre an hour and a half away from Davos. Some 600 people were intercepted there and prevented from leaving for Davos. Police used tear gas to attempt to break up around 300 protesters, according to a police statement.

Some of those people than attempted to mount a sit-down protest in the road, blocking traffic. The demonstrators were put on a train to Zurich, the police said, but immediately pulled the emergency brake cord.

Security had been tight in Davos, with trains barred from stopping at the village's two stations. The only travellers allowed in were those who could show they were on holiday, by carrying skis.

A huge security operation is under way, after the security services were caught out by a violent disturbance at last year's event. Police wouldn't say how many guards were involved this time, other than there were substantially more than in 2000. The police spokesman admitted the security forces had considered firing liquid animal dung at the protesters, but had eventually refrained "on ethical grounds."

Street protests are illegal, because such gatherings required the consent of the local authorities, and they refused to sanction anything during the week of the World Economic Forum's annual meeting.

The spokesman said people had arrived in Landquart by car, coach and train, with the intention of travelling on to Davos.

Guards from a private security firm, as well as armed police and soldiers, manned the compound where the conference is taking place, with barbed wire and attack dogs gurading the perimeter.

More than 100 people had already been turned back from Switzerland because the authorities believed they were planning to join the demonstration.

The Swiss authorities had been desperate to avoid the confrontation which disfigured last year's event, when the local McDonald's restaurant was smashed up. The restaurant appears to have been a target once again this year, though the security services said it was not damaged. Similar violent protests have dogged International Monetary Fund meetings in Seattle and, more recently, Prague.

The campaigners claim the forum is nothing more than a rich man's club, but the event's organisers have tried to present a picture of a meeting where broader aspects of society are represented. Some 36 representatives of Non-Government Organisations, such as Amnesty International, are taking part in the forum.